linux-kernel - [PATCH 4.2.y-ckt 074/268] bcache: allows use of register in udev to avoid "device

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Message-Id: <1453926929-17663-75-git-send-email-kamal@canonical.com>
Date:	Wed, 27 Jan 2016 12:32:15 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Denis Bychkov <manover@...il.com>,
	Kent Overstreet <kent.overstreet@...il.com>,
	Eric Wheeler <bcache@...ux.ewheeler.net>,
	Gabriel de Perthuis <g2p.code@...il.com>,
	Jens Axboe <axboe@...com>, Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 074/268] bcache: allows use of register in udev to avoid "device_busy" error.

4.2.8-ckt3 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Gabriel de Perthuis <g2p.code@...il.com>

commit d7076f21629f8f329bca4a44dc408d94670f49e2 upstream.

Allows to use register, not register_quiet in udev to avoid "device_busy" error.
The initial patch proposed at https://lkml.org/lkml/2013/8/26/549 by Gabriel de Perthuis
<g2p.code@...il.com> does not unlock the mutex and hangs the kernel.

See http://thread.gmane.org/gmane.linux.kernel.bcache.devel/2594 for the discussion.

Cc: Denis Bychkov <manover@...il.com>
Cc: Kent Overstreet <kent.overstreet@...il.com>
Cc: Eric Wheeler <bcache@...ux.ewheeler.net>
Cc: Gabriel de Perthuis <g2p.code@...il.com>

Signed-off-by: Jens Axboe <axboe@...com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/md/bcache/super.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index c70755d..90bd95b 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1966,6 +1966,8 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
 			else
 				err = "device busy";
 			mutex_unlock(&bch_register_lock);
+			if (attr == &ksysfs_register_quiet)
+				goto out;
 		}
 		goto err;
 	}
@@ -2004,8 +2006,7 @@ out:
 err_close:
 	blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
 err:
-	if (attr != &ksysfs_register_quiet)
-		pr_info("error opening %s: %s", path, err);
+	pr_info("error opening %s: %s", path, err);
 	ret = -EINVAL;
 	goto out;
 }
-- 
1.9.1